36 



The Canadian Field-Naturalist 



[Vol. XXXVI 



objection is made to his inroads on my cherries as 

 he more than pays for this destruction by the 

 number of cutworms he consumes in the spring, 

 and one philosophically reflects that acid food is 

 no doubt essential to his internal economy after 

 a steady diet of insects; and perhaps this desire 

 for fruit is analagous to the craving of the woods- 

 men for green food after a winter diet of salt 

 pork. But once, for the good of the colony, I had 

 to destroy a pair of Robins and their brood. 

 Before relating this episode it will be necessary to 

 sketch the contemporary history of a pair of 

 Western Wood Peewees. 



In the summer of 1917, a pair of these birds 

 built their dainty nest on a nearly leafless branch 

 of a small plum tree beside my front door-step 

 and in due course three cream, umber-spotted 

 eggs were laid. It was the first time Peewees had 

 built so close to my house and I was greatly 

 interested. The nest was six feet above the 

 ground and could plainly be seen by one sitting 

 on the verandah. During the first week while 

 the eggs were being laid, the Peewees would fly 

 out when one walked along the path beside the 

 nesting tree, clicking their mandibles together in 

 protests at the intrusion, "gritting their teeth," 

 as one observer humorously put it. It was not 

 long, however, before they became reconciled to 

 their human neighbors and then, at close range, 

 one could watch the female, sitting tight on her 

 eggs, indifferent to the close inspection, while the 

 male, in a nearby tree, drooped his tail, flycatcher 

 fashion, and showed as little concern. Then one 

 morning the eggs were gone who was the culprit? 

 Squirrels and chipmunks had been killed off years 

 before. Magpies and Crows gave my garden a 

 wide berth; could it be traced to the nocturnal 

 activities of white-footed mice? There seemed 

 no satisfactory answer. 



The following year the Peewees returned to the 

 orchard, again built their nest on an exposed 

 branch of the plum tree and as before, laid three 

 eggs therein. Now, under the eaves of the house 

 a few yards from the plum tree there is a small 

 bird-house usually tenanted by Tree Swallows, 

 and on its flat top a pair of Robins had built a 

 nest and raised their young during the summer of 

 1917. These birds also returned the following 

 year and used their old nest on top of the bird- 

 house. Shortly after three eggs of the second 

 setting had hatched and the Peewees' eggs were 

 about seven days advanced in incubation, I was 

 sitting on the verandah steps in the evening dusk 

 relating this Peewee story to a friend when one of 

 the Robins was seen to fly into the plum tree. 

 Immediately there was a commotion of rustling 

 wings and snapping mandibles. The Peewees 



had savagely attacked the Robin and he fluttered 

 to the ground with the Peewees in close pursuit. 

 In a few moments he returned to the tree and 

 hopped along the branch on which the Peewees' 

 nest was built until he stood directly over it, while 

 the Peewees protested from a distance but did not 

 attack again. We waited in breathless excite- 

 ment for the Robin's next move, and to our 

 astonishment, he deliberately pierced one of the 

 eggs with his bill and carried it to the ground 

 where, under a shower of clods, he was forced to 

 drop it. The egg was found intact, save for the 

 puncture made by the Robin's bill. This seemed 

 a clear case against the Robin and the family 

 was condemned. Unfortunately, the sentence 

 could not be carried out that evening, and on the 

 following morning the two remaining Peewees' 

 eggs were gone. 



In this garden-sanctuary, the smaller species of 

 birds, other than those that build in nesting boxes, 

 are the victims of some enemy that takes at least 

 fifty per cent of the first setting of eggs. On one 

 occasion, I counted seven nests that had been 

 rifled of their eggs since the previous day. As the 

 well-known enemies of these birds had been 

 banished, I was forced by a process of elimination 

 to the conclusion that the white-footed mouse 

 was responsible for these raids, but, since I had 

 the experience related above, it would seem that 

 the Robin is not above suspicion as a home- 

 breaker. 



It would be a difficult matter to prove that 

 egg-eating is a habit of the Robin. Egg-eating 

 birds usually discard the egg shells and swallow 

 only the soft embryos or the semi-liquid yolk and 

 albumen. This material is quickly assimilated; 

 consequently the analysis of stomach contents 

 throws little light on this question. The enormous 

 destruction of bird life due to the egg-eating 

 proclivities of the Crow is known to most field 

 naturalists, yet a recent extensive investigation 

 of the economic status of this species, based on 

 stomach analysis, did not furnish proof of the 

 extent of this habit. In the case under discussion 

 where there was the strongest circumstantial 

 evidence that one of the parent Robins had either 

 eaten the Peewees' eggs or else fed them to the 

 nestlings within a few hours of their being killed 

 careful examination of the stomachs of all five 

 birds revealed no trace of the embryos. 



The house-cat is probably responsible for more 

 destruction of insectivorous birds than is any other 

 of the many natural enemies that the sanctuary 

 guardian has to contend with. Domesticated or 

 ferae naturae, full fed or hungry, the cat is a bird- 

 hunter by instinct and by choice. In a small 

 bird-sanctuary where the natural wariness of the 



